Spark plug



Jan- 2, 1934- P. J. FITZGERALD 1,942,242

SPARK PLUG Filed April 7, 1933 Patented Jan. 2, 1934 UNITED STATES SPARK PLUG Patrick J. Fitzgerald, Torrington, Conn., assignor to The Fitzgerald Manufacturing Company,

Torrington, necticut Conn., a corporation of Con- Application April 7, 1933. Serial No. 664,987

7 claims.

The present invention relates to improvements in spark plugs of the type generally used in connection with internal combustion engines, and more particularly the invention relates to the formation and construction of the electrodes thereof.

An object of the present invention is to provide an improved spark plug wherein the electrodes are formed and positioned in a manner designed to give a large sparking area and hence to provide a greater spark than has heretofore been possible.

A further object of the invention is to provide a spark plug of the type referred to, wherein the construction and arrangement of the electrodes' l5 permit a greater wearing surface whereby to render the spark plug more durable.

The invention aims particularly to provide a spark plug, of the type referred to, wherein one -of theelectrodes is provided with an enlarged end in order to increase the spark area.

'Ihe invention further aims to provide an improved spark plug, of the type referred to, wherein one of the electrodes is provided with an enlarged end in which is an arcuate recess which lies adjacent the other electrode and extends partially around the same and equidistant at all points therefrom.

A further object of the invention is to provide an improved spark plug, of the type referred to,

wherein the outer or shell electrode is provided with an enlarged end which is recessed to extend partially around the center electrode at an equally spaced distance `therefrom throughout the entire sparking area.

I'he invention further aims to provide a spark plug, of the type referred to, which is inexpensive to manufacture, which is easily assembled, and which is reliable and eicient`in operation and which is capable of withstanding long wear.

These and other objects of the invention will be obvious and will be hereinafter more fully described.

In the drawing:

Figure 1 is an elevation showing the assembled spark plug.

Fig. 2 is an enlarged bottom plan view showing the arrangement of the electrodes.

Fig. 3 is an enlarged side view, partly in section, showing the position of the electrodes.

Fig. 4 is an enlarged bottom plan view showing another form of electrode.

The invention consists generally in providing a spark plug of the type used in connection with internal combustion engines. 'I'he spark plug is provided with the customary shell and center thickness between the two electrodes.

electrodes which are properly positioned to provide a spark gap therebetween. The center or primary electrode is cylindrical and passes centrally through the usual porcelain insulating member. The shell, secondary or grounded elecy trode is mounted in the lower shell casing and extends downwardly therefrom and is then bent inwardly to lie adjacent the center electrode. This outer or shell electrode is provided with a relatively small end which is mounted in the cast 'engage a, cylinder head opening. The center electrode 12 extends. centrally through the central insulating member 13 to a point below the bottom end of the shell 11. The grounded or shell electrode 14 is of tapering cross-section and may be formed by a swaging, or other operation. The small end 15 is secured in theshell 11 and is bent inwardly below the bottom of the shell to extend toward the center electrode 12. The large end 16 of the shell electrode 14 is provided with an arcuate recess 17 which may be formed by a milling or punching operation. The edge of the recess 1.7 is parallel to the surface of the center electrode 12 and the curvature of the re- 90 cess is symmetrical with the curvature of the center electrode so that the shell electrode is equidistant from the surface of the center electrode at all points.

The enlarged end 16 of the grounded electrode 95 I 14 provides a greater sparking area adjacent the center electrode 12 and also provides a greater wearing surface than has heretofore been employed. The arcuate surface of the recess 17 being concentric with the surface of the center electrode 12 assures a sparking gap of uniform The ends 17 of the recess 17 in thegrounded electrode 14 extend substantially half way around the center electrode.

In Fig. 4 of the accompanyingdrawing, the grounded electrode 18 is provided with an enlarged end 19 which may be formed by upsetting or other process. In this instance the enlarged end 19 is machined to form a recess 20, the end 110 20 of which extends partially around the outer' electrode 12. The recess 20 is equidistant from the center electrode at all points `and is concentric with and parallel to the surface of the center electrode. The same advantages are present in this form of electrode, but the enlarged end is originally formed by a different operation.

From the foregoing description, it is apparent that an eflicient spark plug is herein provided and one wherein the sparking points permit a greater spark and also insure greater wear and longer life because of the increased diameter of the shell electrode at its sparking point.

Of course, minor changes in details of construction and arrangement of parts may be made without departing from -the scope of the invention. f

Having thus fully described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. A spark plug having a center electrode, and a grounded electrode having an enlarged end, said enlarged end having a cross sectional area which is increased in all planes passing through the axis thereof, said grounded electrode having the small end thereof mounted in the shell and being bent inwardly to permit the enlarged end thereof to lie adjacent the ceni er electrode. y

2. A spark plug having a center electrode, and a grounded electrode having an enlarged end, said enlarged end having a cross sectional area which is increased in all planes passing through the axis thereof, said grounded electrode having the small end thereof mounted in the shell and being bent inwardly to permit the enlarged end thereof to lie adjacent the center electrode, the enlarged end of said grounded electrde being provided with a recess the surface of which being parallel to the adjacent surface of the center electrode and extending partially therearound.

3. A spark plug having a center electrode projecting below the shell, and a grounded electrode having a free end of gradually increasing substantially circular cross-section, said grounded electrode having the smaller end thereof secured in the shell and being bent to permit the larger end thereof to lie adjacent the center electrode.

4. A spark plug having a center electrode projecting below the shell, and a grounded electrode having a free end of gradually increasing substantially circular cross-section, said grounded electrode having the smaller end thereof secured in the shell and being bent to permit the larger end thereof to lie adjacent the center electrode, the larger end of said grounded electrode being provided with an arcuate recess the surface of which being concentric with the surface of the 85 center electrode.'

5. A spark plug having a center electrode projecting below the shell, and a grounded electrode having a free end of gradually increasing substantially circular cross-section, said grounded f electrode having the smaller end thereof secured in the shell and being bent to permit the larger end thereof to lie adjacent the center electrode, the larger end of saidfgrounded electrode being provided with an arcuate recess the surface of which being concentric and parallel with the surface of the center electrode.

6. A spark plug having a center electrode projecting below the insulating member, and a grounded electrode mounted at one end in the shell, said grounded electrode being bent to permit the free end thereof to lie adjacent the center electrode, the free end of said grounded electrode being provided with an enlarged portion having a recess therein, the surface of said recess being parallel to the surface of the center electrode and extending partially around the same,` the surface of said recess being co-extensive with the portion of the center electrode projecting below the insulating member.

7. 'A spark plug comprising a primary electrode and a secondary electrode, one of said electrodes being bent to permit the free end thereof to lie adjacent the other of said electrodes, the free end of one of said electrodes having a cross sectional area which is enlarged in all directions from a medial line, said enlarged free end being provided with a recess the surface of which is substantially parallel. to the' surface of the cooperating electrode at all points.

IATRICK J. 

